This invention relates to providing absorbent materials with increased wettability and specifically providing this property of increased wettability in a permanent or substantive manner.
Commonly available absorbent materials such as rayon, cotton, and chemical wood pulp have been used as the raw materials for many commercial absorbent products including, for example, such products for absorbing body fluids as catamenial napkins and tampons, diapers, and surgical dressings. While in the main, such commonly available absorbents have proven useful in such products, in an effort to improve product quality and economy, the art has searched for improved materials. Recently, it has been proposed that the more traditionally employed absorbent materials be, at least in part, substituted for with less expensive absorbents. Examples of these are the relatively inexpensive wood pulps such as thermechanical wood pulp, mechanical wood pulp, and refiner pulp. Further, such non wood pulp absorbents as for example, peat moss and various grasses have been considered. Unfortunately, while these materials have the advantage of reduced cost and are all readily available, they have suffered from the common problem of poor initial wettability as is required for use in body fluid absorbing products.
To correct this deficiency, it is known that certain surface active agents may be applied to these absorbents to provide good re-wetting properties. These agents are typically characterized by the presence of hydrophilic groups in the middle of a hydrophobic chain or as viscus liquids or waxy solids. Such surface active agents are generally classified as cationic agents, anionic agents, nonionic agents, and are all capable of greatly increasing the wettability of the absorbents to which they are applied. Examples of such agents are the alkyl phenols containing sixty to seventy percent polyoxyethylene, alkylsulfosuccinates, and sulfated esters.
Accordingly, surface active agents are known which can greatly enhance the wettability of absorbents and so make them useful in commercial products, it is unfortunate that, heretofore, the surface active agents have lacked the property of substantivity. Said in other words, these agents have not been permanently associated with the absorbent material and as a result have tended to wash out of the material, either during the processing or in use. Accordingly, in a short time, they lose their effectiveness thereby frustrating the purpose of their employment. There is a need, therefore, for a method of providing absorbents with the property of wettability which property is of a permanent or substantive nature.